ID Number		719
Study Type		Epidemiology
Model		Cell phone use by high school students in Hong Kong and correlation with cognitive ability
Details		Human subjects (high school students in Hong Kong) were analyzed for cell phone use (900 MHz GSM) and measures of attention and performance. Of 72 participants in the study, 37 were identified as "mobile phone users" with estimated cumulative phone times between 175 - 27,240 minutes. Mobile phone users performed better on a Trial Making Test, although no differences were observed in a Symbol Digit Modalities Test or a Stroop Color Word Test. No attempt to correlate performance with cumulative cell phone time for a dose response analysis was made. The authors conclude that the observed effects could be due to either an effect of RF facilitating increased attention and performance, but it could be equally possible that the students with mobile phones were otherwise biased (by socio-economic status perhaps) for superior test performance. In a subsequent study, human subjects (n=78, 39 male, 39 female, all right-handed university undergraduate students with no history of neurological illness) were exposed to 1900 MHz (GSM) using a mobile phone hooked-up to the network (unknown power level and SAR) during the first of a 25 minute task (trial making test or sustained attention to response task) followed by a two-minute rest period and a second task with no exposure. For controls, the phone was off during both tasks. The authors report that reaction time in the sustained attention to response task was shorter with exposure (291.67 +/- 35.36 for exposed vs. 305.21 +/- 62.84 for sham). The authors speculate that "attention functions may be differentially enhanced after exposing to the electromagnetic field emitted by mobile phones & furthermore; this transient facilitation effect might be dose dependent". In addition, the authors speculate that "localized heating in the brain may take some time (i.e., about 30 minutes in this case) to trigger heat shock protein production or a vascular response, and could represent a mechanism for enhanced reaction time".
Findings		Effects
Status		Completed With Publication
Principal Investigator		University of Hong Kong - tmclee@hkusua.hku.hk
Funding Agency		Private/Instit.
Country		HONG KONG
References		Lee, TM et al. NeuroReport , (2003) 14:1361-1364 Lee, TM et al. NeuroReport, (2001) 12:729-731
Comments		In the first study, exposure was completely undefined and no adequate controls for the study design or exposure were included. In the subsequent study reported in 2003, the error bars between exposed and control overlap each other significantly, making the statistically significant findings questionable. While the authors claim the study was blinded with respect to the subject knowing whether they were in the exposed group or not, no mention was made of whether a dummy load was placed on the phone during no-exposure to replicate the circuit heating which may have indicated that the phone was on to the subjects during exposure. More importantly, the sequence was not randomized, and the authors admit to a strong learning performance effect during the second test. The researchers assumed (but did not establish by test) that both groups would have had equal baseline pre-test performance and equal learning and performance bias.